The invention relates to the field of fuel cells, more particularly of the air or oxygen and hydrogen type, and more specifically the problem of recovering the water produced by the operation of the cell.
A fuel cell of the above type, formed of at least one element, comprises a cathode compartment comprising an electrode and connected to a fuel supply circuit, which is to say principally air, enriched or not in oxygen. Such an element comprises a second so-called anode compartment containing an electrode which is separated from the first by a membrane for permeation and reaction by means of catalysts that the two electrodes have. Such an anode compartment is connected to a fuel circuit which is the hydrogen.
During operation, a portion of the water formed at the cathode passes through the membrane and enters the anode compartment, more particularly at the outlet of the hydrogen circuit. This outlet is also known to be traversed by the residual hydrogen, nitrogen and impurities.
The water balance of a fuel cell must be ensured such that the quantity of water evaporated by the passage of the gases into the cell will be less than the quantity of water produced by the reaction. This is the reason for which it is of interest to recover the water produced which is at the outlet of the anode compartment. However, the operation of the cell leaves the residual hydrogen in the anode compartment, this hydrogen incorporated in the water requiring the taking of certain precautions to ensure the recovery of this latter under safe conditions.
To observe these requirements, the solution generally used is completely to separate the air-oxygen and hydrogen circuits and to discharge the water produced at the anode outlet by a specific separate outlet.
The water is then lost, whilst the impurities and the nitrogen are eliminated by regular purges of the outlet of the hydrogen circuit.
This non-recovery is not favorable to a suitable hydric balance and this is the reason for which other solutions have been proposed.
One of them envisages injecting the water from the anode compartment at the outlet of the cathode compartment at the same time that a portion of the residual hydrogen mixture, nitrogen and impurities, is injected at the inlet of the cathode circuit.
In this way, the hydrogen is destroyed in contact with the catalyst of the cathode thanks to the presence of an excess of oxygen in the combustible gaseous mixture.
Such a possibility of connection is however not always available as a function of the structural technology of the cell, especially when the air inlet on the cathode side and the water inlet are separated. Moreover, the presence of liquid water at the air inlet can be the cause of disturbance of the flow within the cell. Under these circumstances, it is then necessary to emplace a complicated arrangement of several sets of phase separators in cascade, which complicates the installation of the cell, increases the cost and does not promote continued operation under optimum conditions at a desirable cost.
The object of the invention simply has for its object to overcome the above drawbacks, by providing a new process and new device permitting ensuring recovery of the water produced by the operation of a fuel cell and, more particularly, by that from the anode compartment.
To achieve the above object in the process according to the invention:
position, at the outlet of the hydrogen circuit of the anode compartment, two separators in series, each provided with at least one filter of hydrophilic nature, delimiting in the separator an inlet chamber and an outlet chamber connected to a water evacuation passage,
create a pressure drop in the circuit between the two separators,
provide for continuous passage of fluid from the anode compartment through the separator.
The object of the invention also is, for practicing the above process, a device for recovering the water produced by a fuel cell, of the type comprising at least one element comprised by a cathode compartment provided with an electrode and connected to a fuel supply circuit and by an anode compartment, provided with an electrode separated from the first by a membrane, and connected to a hydrogen supply circuit, characterized in that it comprises two separators disposed in series at the outlet of the hydrogen circuit, each defining at least one separate admission chamber, by a hydrophilic filter, by an outlet chamber connected to the hydric circuit of the cell, a device generating a pressure drop being interposed between the separators.